Security AutoTester is an automated security testing tool designed for automotive software developers, including OEMs and Tier-1 suppliers. It performs fuzz testing and penetration testing against automotive software components such as ECUs and vehicle communication protocols. The tool ships with over 200 pre-built automotive fuzz test cases derived from PlaxidityX's research and prior customer engagements, eliminating the need for users to define test scenarios from scratch. It is designed to be accessible without requiring deep cybersecurity expertise, featuring an intuitive UI/UX. Security AutoTester is built to support regulatory compliance with UN R155 and ISO/SAE 21434 standards, and generates test reports structured to meet regulatory audit requirements. Testing can be applied to a single ECU or an entire vehicle. The tool supports integration into CI/CD development and testing pipelines, enabling continuous security visibility throughout the software development lifecycle. It can also operate as part of a Hardware-in-the-Loop (HIL) simulation environment. Additionally, it can integrate with PlaxidityX's broader DevSecOps platform. Test cases and supported interfaces/protocols are updated continuously to reflect evolving automotive attack surfaces.